A bus bar is a metal strip or bar that conducts electricity and is used for electrical power distribution. Battery cells can be connected with bus bars to make battery packs. Some battery packs using cylindrical cells make electrical connections to the tops and the bottoms of the cells with groups of battery cells having alternating orientations. When connecting cells in series, bus bars and high current interconnects link the positive terminal of one cell, or a parallel group of cells, to the negative terminal of the next cell or the next parallel group of cells. This configuration, illustrated in FIG. 1, obstructs airflow or liquid flow from cooling mechanisms utilized to remove heat generated by the cells, as well as obstructing the space for the cooling mechanisms themselves. FIG. 1 illustrates a schematic diagram of a battery pack 100 with a first group of battery cells 102, 104 in a parallel connection, a second group of battery cells 106, 108 in a parallel connection, and a third group of battery cells 110, 112 in a parallel connection. The first group, the second group and the third group are coupled in a series connection. Bus bars 114, 116, 118, 120 are used to connect the battery cells in this parallel and series coupling. Each of the bus bars is coupled to the respective battery cells with one or more wires, or local soldering or welding. Bus bar 120 couples the negative terminals of the first group of battery cells 102, 104 and is in the electrical direction of the negative terminal for the battery pack 100. Bus bar 114 couples the positive terminals of the first group of battery cells 102, 104 in parallel, and couples the negative terminals of the second group of battery cells 106, 108 in parallel. Bus bar 114 couples the first group of battery cells 102, 104 in series with the second group of battery cells 106, 108. Continuing with the couplings, bus bar 116 couples the positive terminals of the second group of battery cells 106, 108 in parallel, and couples the negative terminals of the third group of battery cells 110, 112 in parallel. Bus bar 116 also couples the second group of battery cells 106, 108 in series with the third group of battery cells 110, 112. Bus bar 118 couples the positive terminals of the third group of battery cells 110, 112 in parallel, and is in the electrical direction of the positive terminal for the battery pack 100. Some of the bus bars 114, 118 are above the battery cells 102, 104, 106, 108, 110, 112, and some of the bus bars 120, 116 are below the battery cells 102, 104, 106, 108, 110, 112. As mentioned above, this creates difficulties for cooling, in that the bus bars 114, 116, 118, 120 may block cooling air flow or may block efforts to install cooling mechanisms. One possibility for cooling is to install a coolant tube in gap 122 between cells 102, 104 in a group of battery cells, as well as other gaps 124 between the cells. For example, a coolant tube may extend in a serpentine fashion between the gaps 122, 124, and so on, of the cells. Such an arrangement can be made with non-uniform spacing between the battery cells 102, 104, 106, 108, 110, 112, such that the battery cells 102 in each pair of battery cells 102 is closely adjacent or touching, but pairs of battery cells 102, 104; 104, 106 are more widely separated by the spacing 122, 124. This spacing configuration consumes a relatively large volume of space.
It is within this context that the embodiments arise.